PlatSil® 71-25 and RTV-4125 are both Shore A25 platinum-cure silicones, placing them in a medium-soft mold range that balances mold support with flexibility during demolding. An A25 profile provides more body than very soft silicone grades while retaining useful flexibility for reusable molds and shaped parts. Actual mold performance still depends on mold thickness, geometry and casting conditions.
The two materials are similar in their basic processing setup. PlatSil® 71-25 uses a 1A:1B ratio by weight, while RTV-4125 uses 1A:1B by weight or volume. Their published working windows are also similar, with approximately 35 minutes for PlatSil® 71-25 and 30–40 minutes for RTV-4125. The mixing systems and stated working times therefore represent relatively small differences between these two products.
Viscosity is also relatively close in the published specifications. Polytek reports approximately 3,500 cP for mixed PlatSil® 71-25, while MinghuiLink reports approximately 4,700±200 mPa·s for Part A of RTV-4125. Because the manufacturers report viscosity at different measurement points and material states, these values should not be treated as a strict like-for-like laboratory comparison. The published figures indicate that both products have different reported viscosity characteristics that should be considered when selecting mixing, pouring and air-removal procedures.
The more significant processing difference is turnaround time. Polytek lists approximately 16 hours for demolding PlatSil® 71-25, while MinghuiLink specifies approximately 4–5 hours for RTV-4125. This difference can materially affect production scheduling and mold turnover. The published demold and cure definitions are not identical, so the figures should be interpreted as manufacturer-stated processing references rather than a direct cure-rate calculation.
The published mechanical data show a different balance. PlatSil® 71-25 reports 418 psi tensile strength, approximately 24.0 N/mm Die B tear strength and 343% elongation. RTV-4125 reports 4.0±0.5 MPa tensile strength, 26±0.5 N/mm tear strength and 460±50% elongation. The published values indicate higher tensile strength and elongation for RTV-4125, while the reported tear values are relatively close. Because the manufacturers use different test methods and data presentation, these figures should be treated as published reference values rather than a strict laboratory ranking.
